1. Field of the Invention
The invention pertains to the field of detection systems. More particularly, the invention pertains to intrusion detection systems using optical image processing techniques.
2. Description of Related Art
The War on Terror that began on Sep. 11, 2001 has drastically changed the American way of life. Terrorism is no longer something that happens to someone else in some other place. The new reality is that any American or American asset is vulnerable to terrorist attack and potential targets range from military bases to city water reservoirs. As the list of potential targets is practically endless, the American manpower and financial resources necessary to protect all these targets can become enormous. To complicate matters, immediate action is needed.
Our terrorist enemies have repeatedly used the cover of darkness for their operations and defense against night operations is extremely difficult. To deny the enemy the use of night cover will be an important step in reducing the effectiveness of his night time operations. A survey of the technology shows that a digital infrared (IR) camera is the prime sensor candidate for such a system.
There are some basic problems with current intruder detection systems that use IR and optical images. They require human operators to observe the images and make the intruder detection decision. This is a very manpower intensive operation with an attendant high overhead cost. Another problem with the manual system is that an intrusion is a rare event. Boredom and human nature will tend to degrade the system effectiveness even under the best conditions of operations discipline. An automatic detection process will provide consistent reliable system performance and reduce the manpower requirements needed to monitor the system operation to a minimum and perform the necessary situation assessments.
There are several methods of automatic motion detection using images that have been used in the past:    1. In the first implementation, the current image is compared against a stored, static, background image. This configuration provides good motion detection but is one prone to high false alarm rates when changes occur in the environment.    2. In the second implementation of comparing the two successive images, the current image is compared to the immediately prior image. Each time a new image is received, the current image replaces this prior image. While this technique works in most cases, there are some problems with this simple frame to frame technique.            (a) An intruder that is moving very slowly may not be detected at all unless the time period between the two successive images is fairly long.        (b) An intruder can move and then stop with the result of a single detection followed by no further detections which could be mistaken for a false alarm. By a series of quick moves followed by long halts, it is possible to penetrate an area without being detected.        
In either case, any noise appearing on either the current image or the prior image, is detected as an image difference. This difference is a false alarm and since noise can appear on either the current image or the previous image, the false alarm rate is doubled in such a motion detection process.